1. Field of the Invention The present disclosure relates generally to passenger aircraft and, more particularly, to aircraft taxiing.
2. Description of the Related Art
In modern passenger aircraft, weight, space, and costs are exceedingly important. It is known that up to 15% of the costs to operate a passenger aircraft are typically spent while the aircraft is on the ground. A significant portion of these costs are for taxiing between airport locations (e.g., gate, hangar, maintenance areas and runway) with power supplied by the aircraft's flight engines.
When flight engines are used for taxiing, they operate in a very inefficient region of their rated thrust and, accordingly, consume substantial pounds of fuel for each minute spent in this operational mode. The resultant fuel costs can be especially substantial at busy airports where aircraft frequently spend extended times between a gate and the runways with the flight engine(s) running. In addition, significant brake maintenance costs are incurred. When the flight engines are used for taxiing, the brakes must be frequently engaged to counter the high thrust of these engines. This significantly increases the frequency of brake repair and adjustment.
Many passenger aircraft also include power systems that provide a number of ground services (e.g., cooling, heating, lighting, hydraulics, engine start, ground system checkout, and emergency power). These additional systems are often referred to as auxiliary power units and emergency power units. Because they add weight to the aircraft while it is in flight, they are another source of added costs.
Any reduction in parts, weight and complexity in aircraft systems is highly desirable. System reliability and maintainability are also important issues, since they impact the availability of an aircraft and its overall costs.